1. Field of the Invention
The present invention relates generally to the fields of semiconductor manufacturing and chemical vapor deposition processes. More specifically, the present invention relates to a method of reducing the electrostatic charge on a substrate during a PECVD process.
2. Description of the Related Art
Plasma enhanced chemical vapor deposition (PECVD) of thin films uses plasma energy to create and sustain the chemical vapor deposition reaction. A radio-frequency (RF) induced plasma source ignites a plasma and creates a plasma field in the deposition gas. The increase in deposition energy enables thin films to deposit at low temperatures and low pressures, thus realizing good film uniformity and throughput.
A PECVD application is performed in a vacuum chamber with a gas distribution means as a top electrode and a substrate support means as a bottom electrode in parallel. These conducting plates are typically several inches apart; the gap is variable to optimize process conditions. Additionally, a radio-frequency power supply is used to supply electrical power between the electrodes to ignite the plasma. A modern reactor is typically a multichamber cluster tool. PECVD is used to deposit thin films onto a substrate that includes, inter alia, flat panel displays, and glass or ceramic plates or disks.
A substrate is supported by a susceptor in the vacuum chamber. The susceptor is a mechanical part of the chamber and functions as a ground or bottom electrode during PECVD processing. Generally, the susceptor has a substrate support plate that is attached to a susceptor shaft and a lift assembly to raise and lower the substrate inside the process chamber.
The substrate is typically an oxide-based material such as glass, quartz, and the susceptor material is an aluminum-based material whose surface is anodized. As an electrostatic charge is built up between two insulators, it is also generated and built up on the backside of a substrate and the top susceptor surface. Thus, during the plasma enhanced chemical vapor deposition of a thin film, both the substrate and the susceptor surface act as insulators.
The electrostatic charge generated during deposition of the film between the substrate and the susceptor surface holds the substrate to the susceptor surface. This charge must be dissipated or removed prior to lifting the substrate from the susceptor surface. Additional steps such as a power lift are used to remove the electrostatic charge. If the electrostatic charge is not properly dissipated prior to separating the substrate from the susceptor surface for unloading, the electrostatic charge can induce substrate breakage when the susceptor moves down. The power lift steps consist of a few steps of gas plasma such as hydrogen that does not affect the deposited film.
The plasma of the inactive gas used for the power lift causes the electrostatic charge on the susceptor support plate and the substrate body to redistribute, thereby limiting the electrostatic attraction between the substrate and the susceptor. Thus, sticking of the substrate to the susceptor support surface is reduced and the substrate is more easily separated from the susceptor support plate. Although this step minimizes losses due to substrate damage, each power lift application requires 15-20 seconds of processing time for each substrate. This additional processing time causes a significant reduction in throughput efficiency and concomitant loss of revenue.
Therefore, the prior art is deficient in the lack of effective means of reducing static charge on a substrate during film deposition. Specifically, the prior art is deficient in the lack of an effective means of using a conductive susceptor to reduce static charge on a substrate. The present invention fulfills these long-standing needs and desires in the art.
In one embodiment of the present invention there is provided a method of reducing an electrostatic charge on a substrate during a plasma enhanced chemical vapor deposition process, comprising the step of depositing a conductive layer onto a top surface of a susceptor support plate disposed within a deposition chamber wherein the conductive layer dissipates the electrostatic charge on the bottom surface of the substrate during a plasma enhanced chemical vapor deposition process.
In another embodiment of the present invention there is provided a method of reducing an electrostatic charge on an oxide-based substrate during a plasma enhanced chemical vapor deposition process, comprising the steps of introducing silane into the deposition chamber; introducing from about 0.5% to about 1.0% phosphine in hydrogen gas into the deposition chamber; igniting the gases with an RF power of about 300 W to about 900 W at a pressure of about 0.3 Torr to about 10 Torr; and depositing a phosphine-doped amorphous silicon conductive layer or a phosphine-doped microcrystal silicon conductive layer onto a top surface of a susceptor support plate; where the phosphine-doped amorphous silicon conductive layer or the phosphine-doped microcrystal silicon conductive layer dissipates the electrostatic charge on the bottom surface of the oxide-based substrate during a plasma enhanced chemical vapor deposition process.
In yet another embodiment of the present invention there is provided a method of depositing a film of material upon a substrate during a plasma enhanced chemical vapor deposition process comprising the steps of introducing a silicon-containing gas into the deposition chamber; igniting the gas under conditions such that a plasma is formed in the deposition chamber; depositing an amorphous silicon conductive layer or a microcrystal silicon conductive layer onto a top surface of a susceptor support plate; positioning the substrate on the amorphous silicon conductive layer or on the microcrystal silicon conductive layer such that an electrostatic charge on the bottom surface of the substrate induced during a subsequent plasma enhanced chemical vapor deposition process is dissipated through the amorphous silicon conductive layer or through the microcrystal silicon conductive layer; and subjecting the top surface of the substrate to a plasma enhanced chemical vapor deposition process thereby depositing the film of material onto the substrate.
In yet another embodiment of the present invention there is provided a method of depositing a film of material upon an oxide-based substrate during a plasma enhanced chemical vapor deposition process comprising the steps of introducing silane into the deposition chamber; introducing from about 0.5% to about 1% phosphine in hydrogen gas into the deposition chamber; igniting the gases with an RF power of about 300 W to about 900 W at a pressure of about 0.3 Torr to about 10 Torr; depositing a phosphine-doped amorphous silicon conductive layer or a phosphine-doped microcrystal silicon conductive layer onto a top surface of a susceptor support plate; positioning the oxide-based substrate on the phosphine-doped amorphous silicon conductive layer or on the phosphine-doped microcrystal silicon conductive layer such that an electrostatic charge on the bottom surface of the oxide-based substrate induced during subsequent plasma enhanced chemical vapor deposition is dissipated through the phosphine-doped amorphous silicon conductive layer or through the phosphine-doped microcrystal silicon conductive layer; and subjecting the top surface of the oxide-based substrate to a plasma enhanced chemical vapor deposition process thereby depositing the film of material onto the oxide-based substrate.
In yet another embodiment of the present invention there is provided a conductive susceptor for use in a deposition chamber for depositing a film of material onto a substrate during a plasma enhanced chemical vapor deposition process, the susceptor comprising a support plate mounted on a shaft, the support plate having an upper surface adapted to support a substrate wherein the upper surface has a conductive material disposed thereon and a lower surface connected to the shaft and interfacing with the shaft.
Other and further aspects, features, and advantages of the present invention will be apparent from the following description of the embodiments of the invention given for the purpose of disclosure.